DESCRIPTION (taken from the application) Insulin dependent diabetes mellitus results from the inflammatory destruction of the pancreatic beta cells. Once these cells are lost they cannot be regained since the mature pancreas has a very poor capacity for regrowth. While there have been major advances in the pancreatic ontogeny field recently, little is known regarding the stem cells that give rise to mature beta cells. If ontogeny of the pancreatic beta cells were better understood, cell replacement therapies could be approached. The overall goal of this application is to identify and characterized pancreatic islet stem cells. This work utilizes the IFN-g transgenic model in which pancreatic islets are continuously regenerating throughout adult life, and pancreatic progenitor cells can be detected. Several approaches will be utilized for marking the progenitor cells in this regenerating model. Cells expressing the homeodomain transcription factors PDX-1, PAX 4, and PAX 6, which are each required for the differentiation of islet cells, will be marked using double transgenic mice harboring the reporter gene beta galactosidase under the regulation of each of these transcription factor promoters. The first set of proposed studies will utilize these marked progenitor cells to perform lineage analysis of the new islet cells within the regenerating pancreas of the IFN-g transgenic mice. The second set of experiments seeks to expand the number of markers for islet stem cells by assessing the expression of a large panel of characterized genes in the primitive pancreatic islet cells and through the production of monoclonal antibodies to these cells. Lastly, we will establish an assay for the stem cell activity of pancreatic progenitor cells by seeding these cells in growth promoting locations in vivo. The insight gaining from this work will expand our knowledge of pancreatic stem cells and increase our ability to purify and assay for these therapeutically valuable cells.